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cfriend · Sep 16th, 2004, 10:37 AM

Hi

I have two questions about grep.

1) Is grep support real time analysis ? What I mean ? I have an application that produces records continuously in a file. I try to run grep but grep run faster my application , it find my requested pattern and exits, but my application still produces records. Is there any way for grep to run continuously and produces results while my application running and produce new records ?

2) Can grep show me only the newest pattern that it finds. For example for a file

aaa1
aaa2
aaa3

and

> grep aaa filename

to show me first the aaa1 , then only the aaa2 and then only aaa3

Thanks

Ashcroft · Sep 16th, 2004, 10:59 AM

Grep is not really appropriate for realtime analysis of a logfile, look for 'swatch' for a daemon that handles this.

If I understand your second question you want unique matches. The usual way to do this in the shell is to use sort and uniq.

(Toggle Plain Text)

$ grep aaa file | sort | uniq

erebus · Sep 16th, 2004, 11:16 PM

In that perticular instance, this would be a little bit more effcient:

(Toggle Plain Text)

$ grep aaa file | sort -u

Ashcroft · Sep 17th, 2004, 3:57 AM

Yeah thats true, I always forget about that -u arg to sort and avoiding an extra process can be very important if the file you grep is huge.

Sep 16th, 2004, 10:59 AM	#2
Ashcroft Programmer Join Date: Sep 2004 Posts: 38 Rep Power: 0	Grep is not really appropriate for realtime analysis of a logfile, look for 'swatch' for a daemon that handles this. If I understand your second question you want unique matches. The usual way to do this in the shell is to use sort and uniq. (Toggle Plain Text) $ grep aaa file \| sort \| uniq $ grep aaa file \| sort \| uniq

Sep 16th, 2004, 11:16 PM	#3
erebus Programmer Join Date: Aug 2004 Location: /dev/null Posts: 65 Rep Power: 5	In that perticular instance, this would be a little bit more effcient: (Toggle Plain Text) $ grep aaa file \| sort -u $ grep aaa file \| sort -u __________________ <span style='font-size:14pt;line-height:100%'><span style='color:red'>"Political power grows out of the barrel of a gun" - Mao Tse-Tung</span></span>

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Sep 16th, 2004, 10:37 AM	#1
cfriend Newbie Join Date: Jul 2004 Posts: 8 Rep Power: 0	Hi I have two questions about grep. 1) Is grep support real time analysis ? What I mean ? I have an application that produces records continuously in a file. I try to run grep but grep run faster my application , it find my requested pattern and exits, but my application still produces records. Is there any way for grep to run continuously and produces results while my application running and produce new records ? 2) Can grep show me only the newest pattern that it finds. For example for a file aaa1 aaa2 aaa3 and > grep aaa filename to show me first the aaa1 , then only the aaa2 and then only aaa3 Thanks

Sep 17th, 2004, 3:57 AM	#4
Ashcroft Programmer Join Date: Sep 2004 Posts: 38 Rep Power: 0	Yeah thats true, I always forget about that -u arg to sort and avoiding an extra process can be very important if the file you grep is huge.

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